Field of the Invention
The present invention relates to a developing roller, a process cartridge, an image forming apparatus, and an image forming method.
Description of the Related Art
One-component developing methods are known as developing methods in electrophotography. One-component developing is known to be an inexpensive developing method having a simple configuration. In one-component developing, there is known a need for applying a high linear pressure to a toner with a regulating blade in order to stabilize conveyance of electric charges.
Examples of the members used in the developing method include a developing roller. For the factor described above, the surface of the developing roller is filmed with the toner component through continued use and cannot maintain the initial state, leading to electric charge conveying ability degradation, which has been the one-component developing method's inherent problem. To this problem, there are known a technique of using a highly releasable material on the surface of the developing roller to suppress filming, and a technique of providing minute concaves and convexes in the surface of the developing roller to reduce the area to contact the filming component.
For example, Japanese Unexamined Patent Application Publication No. 2004-347664 discloses that a surface layer of a developing roller is formed of a cross-linking reaction product of a resin containing a fluorine group and a hydroxyl group and one or more amino resins, and that the object is to prevent toner filming by coating the surface layer of the developing roller with fluorine and to prevent the surface layer from peeling to aim for a longer life of the product.
However, according to Japanese Unexamined Patent Application Publication No. 2004-347664, the developing roller has a poor scraping ability due to the high releasability and cannot reduce adhesion of the toner component and the filming component on a member contacting the developing roller when there is much adhesion on that member. For this reason, this developing roller has not been able to overcome a problem that a streak is generated in the thin toner layer on the developing roller, to eventually generate abnormal images such as longitudinal white streaks on images such as solid images and halftone images.